Adjustable workstand



April 5, 1949. M. B. CONRAD ADJUSTABLE WORKSTAND 4 Sheets-Sheet 1 FiledMarch 50, 1946 1m m" TOR. MARTIN B. CONRAD Agent April 5, 1949. M. B.CONRAD 2,466;155

ADJ US TABLE WORKS TAND Filed March 3O, 1946 4 SheetsSheet 2 INVENTOR.MARTIN B. CONRAD Agent.

April 5, 1949. B, CONRAD 2,466,155

ADJUS TABLE WORKSTAND Filed March 30, 1946 4 Sheets-Sheet 5 69 68 F f i4 INVENTOR. MARTIN B. CONRAD 2 Agent.

April 5, 1949. M. B. CONRAD ADJUSTABLE WORKSTAND 4 Sheets-Sheet 4 FiledMarch 30, 1946 IN V EN TOR. MARTIN B. CONRAD Agent.

Patented Apr. 5, 1949 ADJUSTABLE WORKSTAND Martin B. Conrad, Houston,Tex., assignor to Airquipment Company, Burbank, Calif.

Application March 30, 1946, Serial No. 658,562

8 Claims.

This invention relates to docks or platforms, and relates moreparticularly to work stands usefill in servicing aircraft, etc. It is ageneral object of this invention to provide a practical, portableservice stand of Wide application and having a substantial range ofvertical adjustment.

In the inspection, servicing and repair of airplanes it is necessary toprovide platforms or stands for the workmen. The various models ofairplanes are of different heights and proportions, and it is notfeasible to employ a service stand of fixed height for the servicing andrepair work. For example, the engines of one model of airplane may beseveral feet higher than those of another model, assuming the craft tobe at rest on the field, and a stand that is suitable for the servicingof engines of the first airplane would be useless in the case of thesecond.

It is an important objectof the'present invention to provide a dock orstand of the general character above referred to that is portable tobereadily movable from place to place, and that embodies a work platformcapable of extensive vertical adjustment to be useful in Working uponthe engines and other elements of airplanes of various models and types.

Another objectof the invention is to provide a multiple parallelogramsystem for supporting Work platforms, and other objects, which iscapable of supporting the objectfor true vertical movement withouthorizontal motion. The invention provides a multiplicity ofparallelogram link systems so connected and related that they areoperable to produce vertical elevation and depression of the supportedobject through practically any range of movement without appreciablehorizontal displacement In fact, it is possible to relate the multiplesystems to obtain true vertical movement only.

Another object of the invention is to provide a stand of the classmentioned characterized by :a horizontally stable fluid pressureoperated mechanism for elevating and supporting the'vertlcallyadjustable platform. The above referred to parallelogram link system isprovided with trussing, which stabilizes the same to prevent horizontalinstability, and one or more hydraulic cram units are associated withthe linkage to tefiectnthe vertical movement of the. platform.

Another object of theiinvention is to providea service stand of thecharacter referred tohaving safety means associated with the rams orcylinder and piston mechanism,of-the-platform elevating means, whichprecludes the possibility of accidental dropping or lowering of theplatform.

A further object of the invention is to providea service standincorporating an adjustable stair means providing free access to theplatform at all elevations, the stair means automaticallyadiustingitself to the platform elevation and maintaining its treadshorizontal at all times.

A still further object of the invention is .to provide an adjustable,servicestand of the character mentioned in which provision is made forthereception of the propeller blades of the engine being serviced andfor receiving or draining off oil, etc, from the engine.

Other objects and features of the invention will be readily understoodfrom the following detailed description of a typical preferred form ofthe invention wherein reference will be made to the accompanyingdrawings in which:

Figure 1 is a perspective view-of the adjustable stand provided by thisinventionshowin the platform inan elevated position;

Figure 2 is a fragmentary side elevation showing the parallelogramlinkagefor supportingthe platform;

Figure 3 is a horizontal sectional view taken substantially as indicatedby line 3-93 on Figure2;

Figure .4 is an enlarged longitudinal section .of one of the rammechanisms for elevating the platform, with certain parts appearing inside elevation;

Figure 5 is a horizontal sectional view taken substantially as indicatedby line 5-5 on'Ffgure 4;

Figure 6 is an enlarged fragmentary perspective view of the lowerportion of the stair means;

Figure 7 is a fragmentary front View of the stair means in a fullylowered condition;

Figure 8'is an enlarged fragmentary sectional view taken asindicatedbyline 88 on Figure 7-;

Figure 9 is a diagrammatic view of the fluid pressure system embodied inthe stand; and,

Figure 10 is a horizontal sectional view illustrating the trussing,taken substantially'as indicated by line [0-40 on Figure '2.

The stand or dock of theinvention includes a wheel-supported base frame10 which is generally U-shapedin plan View, having a front portion lland'two rearwardly extending'side portions or beams 12. A steerablewheel i3 is carried-by a trunnion I'I-mounted'midway between the ends ofthe front portion 1 l, and is equippedwithhitch or draftmeans .14" tofacilitate movement of --the stand. Wheels l5'are mounted on axles 16suitered by a perforate grid 23 and equipped with a The grid 23 isprefercommon drain means 21. ably sectional and removable to allow freeaccess to the sump. The sump is adapted to receive oil, water, etc.,from the engine, or other mechanism being worked upon. are notched at 24to receive the propeller blades of large aircraft when the platform isbrought to the required position and elevation under the engine. Thefioor 2| has a removable section 25 aligned with the notches 24 toreceive the propeller blades and to permit the same to pass into thenotches. A workbench 26 may be arranged at the forward end portion ofthe platform I8.

A hand rail 28 is provided for the sides of the platform l8 and issupported by spaced vertical posts 29. A removable chain may be engagedbetween the rearmost posts 29 to form a guard at the rear end of theplatform. Certain of the posts 29 may be bowed outwardly to facilitatethe passage of the propeller blades over the platform structure. Thelower ends of the posts 29 are removably engaged in keepers or sockets||l| set in the platform so that the guard rail assembly and associatedparts may be removed from the platform when desired. The workbench 26extends across the major portion of the platform front and suitablegates}! are provided at the ends of the bench to complete the safetyrail means of the platform. While not essential. canopies may beprovided for the platform l8. n'the drawings the canopies comprisecurved tubes or pipes '30 covered by sections of canvas or other fabric3|;

The lower ends of the pipes 30 are removably engaged in the upper endsof the guard rail posts 29, and the fabric 3| is carried by rolls 32removably engaged in troughs or brackets 33 mounted on the pipes 30. Thetwo canopies are spaced apart to leave a clear area above the removablefloor section 25. It will be noted that the canopies are adapted forindividual removal and in :stallation. v

The means 35 for supporting and adjusting the platform I8 includes amultiple parallelogram system of links at each side of the structure. Inthe invention as illustrated in Figures 1 to 10, there are two likeassemblies, each embodying two The sides IQ of the platform shown themember 4| points on the links 36 and 40.

are pivotally secured to spars I02 at the under side of the platform l8.

In order to synchronize motion of the upper and lower parts of themultiple parallelogram system, and to assure substantially verticalmovement of the platform, I provide a member 4| connected between therear link 31 of the lower parallelogram system and the forward link 39of the upper parallelogram system. The member 4| is pivotally connectedwith the links 31 and 39 at points spaced from their respective pointsof connection with the fore-and-aft link 38. Although I have extendingbetween the links 31 and 39, it is to be understood that the member mayextend between corresponding In the drawings v I have shown the links31, 39 and 40 as box beam parallelogram systems, although the inventionI may be embodied in structures incorporating one or more assemblies,each comprising three or more such parallelogram linkage systems. Eachplatform supporting assembly illustrated in Figures 1 to 10 includes aforward link 36 hinged at members, it being apparent that they may beconstructed of single elements or of several component rod or linkmembers. With the linkage just described, the platform I8 is capable ofvertical movement through a distance of several feet with only a veryminor fore-and-aft displacement, while remaining horizontal at alltimes. It is to be understood that there is a multiple parallelogramsystem of links of the kind just described at each side of thestructure. 7

It is important to brace the assembly to eliminate or reduce to aminimum, lateral movement and displacement of the platform I8 when inall positions. The brace means is preferably a truss arrangementcomprising a substantially rectangular frame comprising the abovedescribed links 38 and front and rear members 44 secured to or engagedbetween the links 38. The front and rear members 44 of the frame arecoincident with the axes of the pivotal connections between the links 38and the links 36 and 31, and if desired, may be utilized as thetrunnions of these connections. Pairs of diagonal trusses 45 arepivotally associated with each member 44, and extend downwardly andlaterally to the side beams of the base I 0 where they are pivotallysecured at 41; see Figure 10. Similar pairs of trusses 48 are pivotallyengaged on the members 44 at 49 and extend upwardly and laterally tohave their upper ends pivotally connected with the side beams IQ of theplatform l8. In practice the truss members 45 and 48 may be identical.In addition to the trusses 4'5 and 48, I provide two braces 50 securedto the forward member 44 adjacent its center-to extend rearwardly andlaterally for attachment, as by welding, to the links 38 adja-- centtheir rear ends. The trussing and bracing just. described are effectivein stabilizing and steadying the structure against lateral deflection,even in cases wheresubstantial loading is imposed on the platforml8.

Fluid pressure actuated means isassociated with the above describedparallelogram linkage assemblies for effecting vertical movement of theplatform I8. Although this means may comprise a single cylinder andpiston unit, I prefer to associate a cylinder and piston mechanism 52with each of the above described linkage assemblies. In the arrangementillustrated in Figures 1 to 10, a cylinder and piston device or rammechanism 52 is connected between the upper rear link 40 and the lowerrear link 31 of each linkage system. The rams 53 of the mechanisms arepivotally connected with the links 40 at points 54 spaced from the lowerends of the links. The cylinders 55 are pivotally connected at theirlower ends to the links 31 at points 51. Assuming the platform Hi to bein a raised position, as shown in Figure'Z.

the points 51 are spaced r'earwardlyfrom the lower pivotal axes of thelinks 31, and the points 54 of the connection of the rams 53 with thelinks 40- are spaced above the upper ends of the links 31. With thisdisposition of the ram mechanisms 52, their loadings are substantiallyconstant though the full movement of the platform l8 and the mechanismsassume substantially horizontal positions when the platform is at thelower extremity of its movement.

The means for supplying actuating fluid pressure to the ram mechanism 52includes a suitable pump 58 preferably mounted on the forward portion Ii of the base. I have shown a pump of themanually operated type providedwith an actuating lever 59. Tanks 60 for the hydraulic fluid or oilemployed are mounted in the boxed base portion l I adjacent the pump. Iprefer to manifold the two ram mechanisms by providing a single fluidpressure system for the two rams; see Figure 9. This com-prises a pipe6| extending from adjacent the pump 58 to the cylinders 55 of themechanisms 52. The pipe 6-1 may be arranged on the inner sides of thebase members H and [2. A single branch pipe 62 extends from the pump 58to the pipe Bl. A manually controllable needle valve 63, or theequivalent, is interposed in the branch 62 so that the operator mayreadily govern the speed of platform movement, especially duringlowering of the platform. A second needle valve- 64, having a fixedsetting, is also provided in the branch pipe 52 to restrict fluid flowand thus retard platform movement in the event the platform is allowedto lower when the valve 63 is fully open.

The ram mechanisms are preferably equipped with ratchet means forretaining the platform l8 at any selected elevation. This means preventslowering of the platform in the event fluid pressure bleeds or leaksaway from the ram units. Referring now to Figures 4 and 5, it will beseenthat a guide bushing 65 of medium soft metal such as Kirksite,bronze, brass, or the like, is fixed in the upper. portion of eachcylinder 55 to surround the ram 53. The" major upper portions of therams 53 are formed with a multiplicity of axially spaced annularserrations, each presenting a fiat normal lower face 66 and a slopingupper face 61. A plate or disc 68 is shiftably engaged on the upper endof the cylinder and bushing, 55, beingretained thereon by guide clips69. The disc 68 has a central opening 10 sufliciently large to. pass theserrations which are cylindrical at their. peripheries. A leaf spring His secured on the cylinder and engages the. disc 68 to urge it to aposition offset from the longitudinal axis of the ram assembly. When inthis offset position the disc 68 is adapted to engage the normal face-66 of any one of the serrations to prevent downward travel of the ram.During upward or out.- ward movement of the ram, the sloping facesratchet past the spring-held'disc and the disc does not interfere withthe free outward travel. However, upon any slight downward travel ofthe. ram 53' the disc 68 engages under a shoulder 66 to prevent furtherdownward movement.

Means. are provided for manually releasing'the ratchet discs 68 to allowdownward movement of the rams 53 and this permit lowering 0f theplatform [8. A bracket 12 is secured on each cylinder or bell crank 13is pivoted in each bracket. The upper arms of the levers 13 cooperatewith the discs 68 and. operating cables 14 are attached to thelowerlever arms. The cables or lines 14 55 and a lever preferably extend tothe forward end of the struc ture and are connected together forsimultaneous operation by a suitable handle I00. The handle or lever M0is adjacent the pump handle 59 and is spring held in a position wherethe dogsor discs 63 are operative to prevent lowering of the platform;see Figure 9. When the operator pulls the cables 14, the discs 68 areshifted to positions in coaxial relation to the rams 53, and the ramsare thus allowed to move downwardly under the control of the valves 62and 64.

The apparatus further includes a vertically extensible stair system topermit free access to the platform l8 when at any elevation. Ahorizontal landing 15 is supported above the forward portion H of thebase 10 and is provided at its edges with parallel guide rails ll. Twospaced pairs of rail members 18 are pivotally suspended from a forwardlyprojecting landing 79 on the platform [8. The members [3 extenddownwardly to the landing l8 and their lower ends are equipped withrollers 88 which cooperate with the tracks IT. A plurality of spacedstair treads 8| are pivotally secured at their ends to the members 18.It will be observed that the stair means just described is an adjustableparallelogram arrangement in which the treads 8| remain horizontal atall elevations of the platform I8. When the platform It is raised andlowered, the rollers 80 ride along the tracks T! and the angularity ofthe members '18 changes, although the treads connected therebetweenpreserve their parallel relationship. The treads 81' are spaced andproportioned to present a substantially continuous fiat horizontalsurface when the platform I8 is brought to its lowermost position asshown in Figure 7. This surface is adapted to form a floor for theworkmen.

A hand rail 83 is provided for the stair means.

,The rail 83 is parallel with the members 18 and is pivotally supportedat its lower end by a post 84 associated with the lowermost tread 8|.The upper end of the rail 83 is pivotally attached to a guard railstructure 85 on the landing 19. It will be observed that the rail 83 atall times remains in an operative position parallel with the members18-.

I prefer to provide a second stair means to facilitate access to theplatform F6. This means includes a support or bracket 86 mounted at theunder side of the landing T5 by a vertical hinge pin 31. The bracket 86has a horizontal proje ction 88 forming the upper step or tread of thesupplemental stair means. Two spaced pairs of spaced rail members 89 arepivotally secured to opposite edges of the projection 88. The outerorforward members 8.) are adapted to rest on the ground or field when thestair is extended but the rear members 89 terminate some distance abovethe ground. Spaced treads 93 are secured at their ends to the members 89by pivot pins 9|. The members 89 and treads $9 form a parallelogramlinkage capable of adjustment to conform with the ground level, etc.,while maintaining the treads 90 horizontal. The stair system is capableof being raised to a horizontal position. where it is fully collapsed.Notches 92 are formed. in the upper edges of the rear members 39 toreceive the hinge pins 9| at the forward edges of the treads 90 andprojection 88 when the assembly is thus raised. To condition the standfor movement across the field, it is usually preferable to raise thestair means just described, to a. horizontal position where it is fullyfolded, and. to then swing the collapsed assembly rearwardl'y 7 aboutthe hinge pin 81. This brings thefolded, stair under the landing 16where it leaves the forward end of the stand free and unobstructed.

Suitable ground engaging pads 93 are provided on the side beams IQ ofthe base 10. These pads may be of any selected type, but are preferablyadjustable to conform with the ground level and to compensate forvariations in height of the loaded base [0. The pads 93 serve tostabilize the.

base when the stand is in use.

From the above detailed description it will be seen that I have provideda practical adjustable work or service stand having extensive utility.The platform l8 may be raised to any required height by simply operatingthe pump 58, and the ratchet disc 68 automatically locks the rams 53 inthe required elevated positions. The multiple parallelogram linkagesassure vertical movement of the platform 58 with a minimum horizontaldisplacement, and the trussing associated with the linkages preventslateral deflection and the tipping of the platform. The platform remainshorizontal and stable at all elevations, constituting a dependable standfor the servicing of airplane engines, etc. The stair means follows theplatform l8 throughout its full range: of movement While preserving thetreads 8| in horizontal planes, thus providing for ready access to theplatform at all times. ages and trussing are such that the platform maybe lowered by control of the valve 53 to a horizontal position at orimmediately above the base Hi With the platform I8 in this extremedownward position, the stair treads 8| form a flat horizontal landingfrom which either gate 8 may be easily reached.

Having described only a typical form of the invention, I do not wish tobe limited to the specific details herein set forth, but wish to reserveto myself any variations or modifications that may appear to thoseskilled in the art or fall within the scope of the following claims.

I claim:

The combination of a base, a platform above the base, a multipleparallelogram linkage supporting the platform on the base for verticalmovement comprising a pair of spaced lower links pivoted on the base, apair of spaced upper links pivoted to the platform, means pivotallyconnecting the corresponding links of said upper and lower pairs, a linkmember substantially parallel with the base extending between andconnecting the two pairs of links at said means, and a tension memberextending between and pivotally connected with a lower link and an upperlink to restrain the platform against appreciable horizontal movementduring vertical movement thereof, and means for moving the platformvertically.

2. A device of the character described comprising a substantiallyhorizontal base, a substantially horizontal platform above the base, amultiple parallelogram linkage supporting the platform on the base forvertical movement including a lower forward link pivoted to the base,

a lowerrear link pivoted to the base, an upper.

forward link pivoted at its upper end to the platform and pivotallyconnected at its lower end with the upper end of the lower forward link,an upper rear link pivoted at its upper end to the platform andpivotally connected at its lower end with the upper end of the lowerrear link, a link member pivotally connecting said four links at thepoints of pivotal connection of the, upper links with the lower links,and a tension The parallelogram linkmember extending betweenandpivotally cong nected with the lower rear link, and the upper"forward link to restrain, the platform against horizontal movementduring vertical movement.

thereof, and means for,movingthe platform vertically.

. 3. A device of the character described comprising a substantiallyhorizontal base, a sub.-; stantially horizontalplatform above the base,a multiple parallelogram linkage supporting the platform on the base forvertical movement including a lower forward link pivoted to the base,

a lower rear link pivotedto the base, an upper: forward link pivoted atits upper end to the plat--. form and pivotally connected at its lowerend; with the upper end of the lower forward link,

an upper rear link pivoted at its upper end to,

the platform and pivotally connected at its lower end with the upper endof the lower rear link,: a link member pivotally connecting said fourlinks at the points of pivotal connection of the upper links with thelower links, and a tension member extending between and pivotally con-,

nected with the lowerrear link and the upper ment, said systemsincluding pairs of upper andv lower links, and pivotal connectionsbetween the links of each pair, truss means connected with the linkagesystems and with the base and platform for stabilizing the platformincluding hori-..

zontal members coincident with the axes of said connections, anddiagonal members extending from said horizontal members to the base andplatform, and means for moving the platform vertically.

5. A device of the character described comprising a base, a platformabove the base, spaced multiple parallelogram linkage systems supporting the platform on the base for vertical .movement, a cylinder andpiston mechanism associated with said systems for moving the platformvertically, ratchet means for preventing retrograde movement of thepiston of said mecha-. nism to retain the platform in any selectedposition and manually operated means for releasing the ratchet meansincluding a flexible operating line extending to a point remote from thecylinder and piston mechanism.

6. A device of the character described com-. prising a substantiallyhorizontal base, a substantially horizontal platform above the base, a

multiple parallelogram linkage supporting the platform on the base forvertical movement inlinks at the points of pivotal connection of theupper linksv with the lower links, and a tension member extendingbetween and pivotally connected with the lower rear link and the upper.forward link to restrain the platform against horizontal movement duringvertical movement thereof, and a cylinder and ram mechanism connectedbetween one of the lower links and one of the upper links for moving theplatform vertically.

7. A device of the character described comprising a base, a platformabove the base, means supporting the platform on the base for verticalmovement, means for moving the platform vertically, a landing on thebase, pairs of parallel members pivoted to the platform and extendingdownwardly to the landing, spaced horizontal stair treads pivoted to themembers to remain horizontal during vertical movement of the platform,and means supporting the members on the landing for free horizontalmovement during vertical movement of the platform.

8. A device of the character described comprising a base, a platformabove the base, means supporting the platform on the base for verticalmovement, means for moving the platform vertically, a landing on an endof the base, pairs of parallel members pivoted to the platform andextending downwardly to the landing, spaced horizontal stair treadspivoted to the members to remain horizontal during vertical movement ofthe platform, and roller and track means supporting the members on thelanding for free 10 horizontal movement during vertical movement of theplatform.

MARTIN B. CONRAD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 233,788 Mitchell Oct. 26, 18801,112,543 Love Oct. 6, 1914 1,595,450 Christian Aug. 10, 1926 1,718,979Protzeller July 2, 1929 2,064,445 Nilson Dec. 15, 1936 2,176,636 MeachamOct. 17, 1939 2,201,189 Makaroff et a1 May 21, 1940 2,354,905 Bailey eta1. Aug. 1, 1944 2,370,887 Soskin Mar. 6, 1945 2,402,579 Ross June 25,1946 2,411,966 Hogan Dec. 3, 1946 2,414,684 Wohlforth Jan. 21, 19472,430,179 Lanchester Nov. 4, 1947 FOREIGN PATENTS Number Country Date521,924 Great Britain June 4, 1940

